Articles tagged recipe

PostgreSQL notifications with Psycopg2 and Eventlet

Posted by Daniele Varrazzo on December 1, 2010
Tagged as async, eventlet, notify, recipe

PostgreSQL supports asynchronous notifications, a simple messaging system allowing clients to be notified about events occurred in the database. Notifications can be sent by any session using a "NOTIFY channel" command and will be received by any session which has subscribed with a LISTEN channel to receive updates. The system has been greatly improved in PostgreSQL 9.0 with the addition of a message payload, making the feature even more useful. Previously a typical use case would have been to notify interested sessions that a certain table was updated: now it is possible to signal for instance which record was changed. You can put the NOTIFY command in a database trigger for automatic notifications on insert or update... the possibilities are actually quite interesting.

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Links about building Psycopg on Mac OS X

Posted by Daniele Varrazzo on November 11, 2010
Tagged as os-x, recipe

Looks like building Psycopg on OS X is tricky: the code needs no tweak, but linking against the right library seems problematic.

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Passing connections to functions using a decorator

Posted by Daniele Varrazzo on October 22, 2010
Tagged as recipe

In many script I write, there are functions requiring database operations. Every time I need them, I try to write such code in functions like:

@with_connection
def do_some_job(cnn, arg1, arg2=None):
    cur = cnn.cursor()
    cur.execute(SQL, (arg1, arg2)) # or something else

do_some_job(42, arg2='hi')

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